<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <!--将网页视口设置完美视口-->
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="x-ua-compatible" content="ie=edge">

    <title>Title</title>
</head>
<style>
    *{
        margin: 0;
        padding: 0;
    }
    html{
        font-size: 13.333333vw;
    }
    .box1{
        width: 7.5rem;
        height: 0.35rem;
        background-color: #f00;
    }
</style>
<body>

<div class="box1"></div>
</body>
</html>
